Spark-plug



C. S. DELANO.

SPARK PLUG.

APPLICATION FILED JULY 13, 1917.

1,370,789 Patented Mar. 8, 1921.

UNITED STATES PATENT OFFICE.

CA RL S." DELAN O, OF BALTIMORE, MARYLAND, ASSIGNOR OF ONE-HALF T0 ROBERTR.

MACGILL, 0F GATONSVILLE, MARYLAND.

SPARK-PLUG.

T 0 all whom it may concern:

I Be it known that I, CARL S. DELANO, a citizen of the United States, residing at Baltimore, in the State of Maryland, have invented certain new and useful Improvements in Spark-Plugs, of which the following is a specification.

This invention relates to improvements in spark plugs for effecting the ignition of the gases in internal combustion engines.

The main object of the invention is to provide an improved spark plug so constructed that those parts which are exposed to the interior of the cylinder and where the spark gap is located may be bodily removed and replaced by new parts without the necessity of renewing the entire plug.

In the use of spark plugs, failure in the plug to produce a spark is due to troubles at the gap and caused by one thing or another. The remainder of the plug is as good as when new, but owing to the construction of the plug" it is often necessary to stand the loss of an entire plug to remedy the difficulties.

' One object therefore of the present invention is to provide a plug of novel construction that will permit the greater portion of the plug to be retained and enable a unit at the inner end of the structure to be detached and replaced by a new unit that carries both points that form the spark-gap, whereby the expense of renewal will be very materially lessened and reduced to the cost of a new unit.

The invention is illustrated in the accompanying drawing, wherein,-

Figure 1, shows the improved plug in longitudinal section.

Fig. 2, illustrates a cross-sectional detail through the same,the section being taken on the line 22 of Fig. 1. A

Fig. 3, illustrates the outer permanent portion of the plug in side elevation, and

Fig. 4, illustrates the inner detachable unit or renewable portion of the plug.

Referring to the drawing, the numeral 5, designates the central body portion of the plug formed of suitable insulating material, and in the present instance having an enlarged inner portion 6, which is circular in exterior outline and which is provided with a central cavity 7. The outer end 8, of the insulating body in this instance is slightly tapered and is preferably circular in crosssection.

Specification of Letters Patent.

Patented Mar. 8, 1921.

Application filed July 13, 1917. Serial No. 180,277.

An electrode 9, extends centrally through the lnsulating body but, in the present instance, is of less length than the body and terminates in a central passage 10, for a purpose that will presently be explained. The passage 10, extends from the inner end of the electrode 9, to andopens at the central cav- 1ty 7 so that a yielding contact stem 11, with a head 12, on the lower end thereof may proect up into said passage and have a longitudinal movement in the latter. The head 12, of this stem is movably located in the central cavity 7, and a spring 13, of conductmg material, is confined in the passage 10, and is interposed and compressed between the end of the electrode 9, and the end of the stem 11, said spring pressing the stem 11, in a dlrection toward the cavity 7, and serving as a conductor for an electric current between the stem and electrode.

The outer end of the electrode 9, is provided with any suitable device or construction 14, by which it may be readily connected to a wire.

A metal cap 15, embraces and completely incloses the inner enlarged portion of the insulating body and has a tapered opening 16, in its upper end through which the tapered end 8, of the body projects. The cap and insulating body are rigidly united by any suitable means, such for example as by means of a screw or pin 17 passing through the side of the cap and entering a recess in the side of the body.

The inner end of the cap has an exteriorly threaded sleeve portion 18, for screwing into the usual threaded opening in the cylinder of the engine, andin the present instance, the inner annular wall of'this sleeve is provided with screw threads 19, for a purpose that will presently be explained.

The inner end of the lug is provided with a detachable unit or head 20, having a cavity 21, in its lower or inner side, and pro vided with a reduced plug 22, at its outeror upper side, which forms an annular shoulder 23, around the head at the base of the plug. The reduced plug 22, of this unit or head is provided with exterior threads 24, which extend down to the shoulder 23, and the diameter of the threaded plug is such as to screw into the inner annular threaded wall 19, of the cap. I

The detachable unit or head is provided with a central screw-threaded opening 25, that extends from the cavity 21, all the way throu h the plug portion 22, and an insulating p ug 26, is rigidly and permanently secured in said opening 25, and has one end 27, projecting from the plug into the central cavity 7, of the outer insulating body and its other end 28, projecting inwardly into the cavity 21, at the inner end of the detachable unit or head.

An electrode 29, is carried by and extends through the insulating plug 26, and the outer end of this electrode is provided with a head 30, which is exposed in the cavity 7, and which contacts with the head 12, of the yielding stem 11 also in said cavity, whereby to make electrical connection with the latter. The other or inner end 31, of the electrode 29, projects at the inner end of the insulating plug 26, and has permanent position at the inner side of the detachable unit or head 20.

A contact pin 32, is also permanently attached to and carried by the detachable unit or head 20, and is projected toward the end 31, of electrode 29, but is sufiiciently spaced from the latter to form the required gap 33, across which the current jumps to produce a s ark in the usual manner.

rom the foregoing explanation it will be understood that when the detachable ufiit or head 20, has its threaded plug 22, screwed into the interior of the sleeve portion 18, of the cap, the head 30, of electrode 29, will contact with the head 12, of the yielding stem 11, and move the latter against the action of the spring 13, and toward the rigid electrode 9, thereby completing the contact from one stationary electrode 9, through the spring 13, to the other stationary electrode 29.

Itwill also be seen that when the permanent and detachable unit of the plug are screwed together, ample space or gap is provided between them by reason of the cavity 7, to prevent a short circuit, should gap 33, become closed by adhering carbon, and it will also be seen that the stationary insulating lug 26, by projecting into the cavity 7, e ects an overlapping condition of the insulating plug with the insulating body and thereby prevents the formation of a direct gap between the central electrodes and the grounded metallic cap so that short circuiting is practically impossible.

It will further be noted that when the detachable unit or head is screwed into the threaded sleeve of the cap all access of gases or products of the cylinders will be kept from the central electrode conta'ctsand stem and interference with these contacts from such causes will be entirely avoided.

If spark-plug troubles are experienced and it is deemed advisable to provide fresh and new points, it is only necessary to remove the plug, unscrew detachable unit or head 20, which permanently and rigidly carries both spark-gap contacts, and screw on a new unit or head, thus making use of the good parts of the plug and only renewing the unit giving the trouble.

By means of this invention, the cost of maintenance of spark-plugs is very materially reduced.

It is to be understood that the renewable or detachable head forms a unit, in that it carries permanently connected electrodes, with a fixed relation with respect to each other, so that one unit, carrying both electrode-points, may be attached and detached as a whole, and without any adjustment of the electrodes with respect to each other.

Having described my invention what I claim is,

In a spark plug, the combination with an outer metallic casing with an electrode therein, said casing having an externally-threaded end to engage a cylinder wall, of a closed head having a cavity at its inner end; an insulating plug permanently attached to and extending through the closed head with the inner end of the plug projecting into said cavity; an electrode extending through the plug; a metallic device extending across the inner end of the head-cavity to form a spark-gap with the end of the plug electrode,-said head, plug, plug-electrode and metallic device all being permanently united to form a unit, and means for detachably connecting the said unit to the metallic casing, with the unit projecting inwardly beyond the external threads of the casing.

11 testimony whereof I afiix my signature in the presence of two witnesses.

CARL S. DELANQ. Witnesses:

Cnanmns B. MANN, Jr., Roaan'r R. MACGILL. 

